Means and method for controlling surface resolution at certain points on members of figures produced in an electronic image generator



Aug. 5, 1969 L. HARRISON m 3,45 9

MEANS AND METHOD FOR CONTROLLING SURFACE RESOLUTION AT CERTAIN POINTS ON MEMBERS OF FIGURES PRODUCED IN AN ELECTRONIC IMAGE GENERATOR Filed Jan. 12, 1968 2 Sheets-Sheet l OR GATE '46 GATE MUUT 44 Z66 THREE 4 27 COORDINATE PARAMETER 57 Z90 VOLTAGE Q .36 20 GENERATOR FOR M AXIAL VECTORS M f 28 co SINE ROTAT/ONAL 71 2 TRANSFORM OR GATE 1 26 6 f 29 797 M 789 MULZ' GENE RA-TOI? 0F VOLUME TR/C VECTOR -THRE L699 24 co OPDINATE$ 62 27 30 I 0/5 PL A) MULI OSCILLOSCOPE /A/\/EI/ TOR:

LEE HAQR N111 6/ MW. gIAW-MW I F LTEQ 0 10 7 699 z 705 7 Aug. 5, 1969 L. HARRISON 3,459,99

MEANS AND METHOD FOR CONTROLLING SURFACE RESOLUTION AT CERTAIN POINTS ON MEMBERS OF FIGURES PRODUCED IN AN ELECTRONIC IMAGE GENERATOR Filed Jan. I 12 1968 2 Sheets-Sheet 2 2 RMS DETECTOR 65 Low PASS I1 I79 RMS 708 7 DETECTOR m9 103 m R 2 RMS 4 DETECTOR TIME TIME I I 0 VELOCITY 0 T/ME RECTIFIER 7 at Y 130 IN/ENTOE! LEE HARE/SOME United States Patent U.S. Cl. 315-18 8 Claims ABSTRACT OF THE DISCLOSURE A network for maintaining substantially constant resolution of surfaces of varying cross-section on a display produced by an electronic image generator.

RELATED APPLICATIONS This application is a continuation-in-part of Lee Harrison III application Ser. No. 607,078, filed I an. 3, 1967, now U.S. Patent No. 3,364,382, which was a continuation of application Ser. No. 240,970, filed Nov. 29, 1962, now abandoned.

BRIEF DESCRIPTION OF THE INVENTION In the Lee Harrison III patent, D.C. voltages corresponding to the X, Y and Z angular coordinates of the basic axial vector or bone of a physical member to be displayed are integrated. The outputs from the integrators are ramp functions of time corresponding both to angular and length coordinates of the member in the three dimensions. As these ramp functions are generated, a high frequency voltage is vectorially added to the ramp function voltage. The high frequency voltage corresponds to the loci of points on the surface or skin of the member. As the Lee Harrison III patent describes, this high frequency vector is generated in synchronization with the generation of the parameters corresponding to the length and angular coordinates and, in the Lee Harrison III patent, the generation of both parameters and the high frequency vector voltages are normally done at constant rates.

When the generation of the high frequency vector voltage is synchronized with the generation of the basic axial vector skin resolution is constant throughout the length of the member only if the cross section of the member is constant (e.g. the linear surface increments parallel to the axis of the members are constant). Skin resolution changes significantly, and may be poor when drawing such things as the flat end of a cylinder, the rounded end of some other member, or other irregular surfaces.

The aforesaid Lee Harrison III patent contemplates the incorporation of means to maintain proper skin resolution for variations in the cross section of surfaces being drawn, and the present invention provides such means.

In general, the present invention provides a network for controlling the rate of generation of the basic axial vector so that the high frequency skin vector can be generated and added to the basic axial vector, the skin vector being modulated to correspond to the changing surface caracteristics which require the controlled generation of the axial vector. Means are described for completely stopping the axial vector and for only retarding its generation, depending upon the surface which is to be drawn.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic diagram of a network for controlling the rate of generation of the basic axial vector;

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FIGURE 2 is a schematic diagram of a network for generating the average longitudinal derivative of the high frequency volumetric vector for use in the network of FIGURE 1;

FIGURE 3 is a schematic diagram of another network for generating the average longitudinal derivative of the high frequency volumetric vector;

FIGURE 4 is an amplitude-time diagram representing the wave form of the volumetric vector for drawing a vase;

FIGURE 5 is a derivative-time diagram of the wave form representing the derivative of the wave form of FIGURE 4;

FIGURE 6 is a diagram of the negative rectification of the wave of FIGURE 5;

FIGURE 7 is a schematic diagram of another network generating the average longitudinal derivative of the high frequency volumetric vector as developed in FIGURES 4-6.

DETAILED DESCRIPTION OF THE INVENTION FIGURE 1 shows the three bone integrators for X, Y and Z components of the basic axial vector or bone 265, 266 and 267 comparable to those shown and described in the Lee Harrison III patent with the same numbers respectively. The integrator 265 has a high gain amplifier 268 and integrative capacitor 269. Similarly, the integrator 266 has an amplifier 270 and a capacitor 271, and the integrator 267 has an amplifier 272 and a capacitor 273.

In the aforesaid Lee Harrison III patent, means are described for generating the three coordinate voltages supplied in conductors 277, 287 and 292, respectively, to be integrated in the integrators 265, 266 and 267. Such gencrating means, which may be thought of an a three coordinate parameter voltage generator for axial vectors collectively designated by the reference character 10, are shown in FIGURE 1 with the output conductors 277, 287 and 292. However, in this application, the conductors 277, 282 and 292 are connected to multipliers 12, 13, and 14, respectively, for purposes to be described.

As in the Lee Harrison III patent, there are output conductors 280, 290, 294 from the integrators 265, 266, and 267, and these conductors lead to summers 16, 17 and 18, respectively, having output conductors 19, 20, and 21 connected to a sine-cosine rotational transform 739 corresponding to the camera angle network 739 of that application. Output conductors 789 and 797 from the transform 739 carry signals to control the horizontal and vertical deflection of the beam of a display oscilloscope 22 corresponding to the display tube 11 of that application.

In the Lee Harrison III patent, other conductors to the adding networks corresponding to the summers 16, 17, and 18 carry voltages representing the three dimensional coordinates of the high frequency volumetric or skin vector, and means for generating such voltages as described. Such a means, which may be referred to as a generator of volumetric vector-three coordinates 24, and the corresponding conductors 698, 699, and 700 are shown in FIGURE 1 of this application. However, instead of being connected directly to the summers 16, 17, and 18, the conductors 698, 699, and 700 are respectively connected to multipliers 25, 26, and 27 for purposes to be described, and the output conductors 28, 29, and 30 are connected to the summers 16, 17, and 18.

A conductor 33 leads to the integrator 265. The conductor constitutes the output from a gate 34 having as an input a conductor 35 connected to the output from the multiplier. A similar conductor 36, gate 37, and conductor 38 are connected betwen the integrator 266 and 3 the multiplier 13, and a conductor 39, gate 40 and conductor 41 are connected between the integrator 267 and the multiplier 14.

The gates 34, 37, and 40 are controlled by conductors 43, 44 and 45 which are connected by a common line 46 to the output of an or gate 47. An input conductor 48 to the or gate 47 leads from an analog or gate 48 which has input conductors 49 and 50 leading from separate parameter gates 51 and 52. The parameter gate 51 is connected in a chain of parameter gates corresponding to an end member of a display figure, such as the chain of parameter gates 69, 70, 71, and 72 of the aforesaid Lee Harrison III patent; and is opened by a signal in an input conductor 53 to pass a voltage established by another input conductor 54; the parameter gate 52 is connected in another chain of para-meter gates, such as correspond to the gates 77, 78, 79, and 80 of the Lee Harrison III patent, and is opened by a signal in an input conductor 55 to pass a signal established by another input conductor 56. There may be additional gates corresponding to the gates 51 and 52 corresponding to additional end members or bones. Preferably, these gates 51 and 52 are each operated by a flip-flop such as the flipfiops 57, 58, 59 and 60 in a control flip-flop network of the kind set forth in an application of Lee Harrison III entitled Means and Method for Interlocking Volumes at .Tunctures Between Members of an Electronic Image Display and for Controlling Reversal of Signals Upon Generation of the Last of 21 Sequence of Members in an Electronic Image Display, filed Jan. 15, 1968, Ser. No. 698,017.

The multipliers 25, 26, and 27 have additional input conductors 60, 61, and 62 which are connected to a common line 63 connected to the output of an integrator 64. The integrator 64 has an amplifier 65 in parallel with a capacitor 66 that has a switch 7 connected across it. The switch 7 is normally closed to discharge the capacitor 66, but is opened when there is an appropriate signal in a conductor 68. The conductor 68 is connected to the output side of the analog or gate 48.

An or gate 70 is connected to a conductor 71 on the input side of the integrator 64. The or gate 70 is supplied by two conductors 71 and 72 that are connnected to the outputs of two gates 73 and 74. The gate 73 is operated by the same input signal in the conductor 53 as the gate 51. A signal in the conductor 55 operates the gate 74. Other input conductors 75 and 76 establish the signals passed by the gates 73 and 74.

There is another input conductor 79 to the or gate 47. This conductor 79 is connected to a suitable source of signals (not shown) for holding the voltages in the integrators during calculation periods or for any other desired purpose.

Also, there are additional conductors 80, 81, and 82 connected as inputs to the multipliers 12, 13, and 14, respectively. These conductors 80, 81, and 82 are connected to a common line 83 that carries signals from other networks, such as those shown in FIGURES 2, 3, and 7.

In FIGURE 2, a network 100 for obtaining the average longitudinal derivative of the variations of the surface from being parallel to the basic axial vector of a member. In FIGURE 2, there are three RMS detectors 101, 102, and 103 which produce signals in their output conductors 104, 105, 106, respectively, proportional to the areas of their rectified sinusoidal input. The inputs to the RMS detectors 101, 102, and 103 comprise the three-dimensional coordinate voltages of the volumetric vector in the conductors 698, 699, and 700 respectively. The output conductors 104, 105, and 106 are connected to a summer 107 which has an output conductor 108 leading to a variable voltage attenuator 109. The variable voltage attenuator 109 is adjusted to produce an output voltage within the range of to 1 as proportioned to its 4 input. This output voltage is supplied by the conductor 83 to the multipliers 12, 13, and 14 of FIGURE 1.

FIGURE 3 shows another network for producing the average longitudinl derivative. In this network 115, there is a low pass filter 116 which is fed signals by a conductor 117 corresponding to a modulated high frequency volumetric or skin vector. The modulated skin vector may be produced by any suitable means, such as is described in the aforesaid Lee Harrison III application as supplied in the conductor 349 of FIGURE 4 of that application. The low pass filter 116 passes the low frequency signals of its input and filters the rest. Its output conductor 118 is connected to a variable voltage attenuator 119 that produces an output in the range of 0 to 1 proportioned to its input. This output is supplied by the conductor 83 to the multipliers 12, 13, and 14 of FIGURE 1.

FIGURES 4, 5, and 6 show the development of a negatively rectified wave form as produced in another network 125, shown in FIGURE 7. FIGURE 4 shows the volumetric or skin vector wave form 126 for drawing a vase. FIGURE 5 shows the derivative 127 of the wave form 126 and FIGURE 6 shows the negatively rectified wave 128 corresponding to the wave form 127. This approach will work for any display subject that has a crosssection that is substantially constant at any transverse plane (normal to the basic axial vector) even through the cross-section may vary longitudinally. A vase is an example of such a display subject.

In the network of FIGURE 7, the volumetric vector corresponding to the signal in the conductor 349 of the aforesaid Lee Harrison III Patent No. 3,364,382 (and to FIGURE 4) is supplied by a conductor 130 to a ditferentiator 131. The output signal from the differentiator (corresponding to FIGURE 5) is fed by a conductor 132 to a rectifier 133 the output of which is a negative rectification corresponding to FIGURE 6. This output is supplied by a conductor 134 to a variable voltage attenuator (or amplifier) 135 which is adjusted to produce a voltage signal in the range of 0 to 1 proportional to its input. This signal is supplied to the conductor 83 leading to the multipliers 12, 13, and 14 of FIGURE 1.

OPERATION First the procedure for holding the outputs from the integrators 265, 266, and 267 constant will be described. It is understood that whenever the gates 34, 37, and 40 are open, there is no signal going into the integrators 265, 266, and 267, and thus, the charge already on the capacitors 269, 271, and 273 remains unchanged. Therefore, the X, Y, and Z signals in the conductors 280, 290, and 294, respectively, will remain unchanged during the time these hold gates 34, 37, and 40 are held open. Thus, one method of controlling the velocity, namely making the velocity zero, of the point which is moving along the bone, is to prevent any new signal from getting to the integrators 265, 266, and 267.

An appropriate voltage is introduced into the input conductors 54 and 55 to the gates 51 and 52, respectively, during the time that the particular bones represented by these parameter gates 51 and 52 are being drawn. These bones would typically be what can be called end bones which have surfaces which have to be put on the ends of bones, these surfaces being generally perpendicular or orthogonal to the bone. When the gate 51 is opened by virtue of its bone control flip-flop, an appropriate signal is introduced into the conductor 49 which goes through the analog or gate 48', the conductor 48 the or gate 47 and into the branch conductors 43, 44, and 45. This signal is such that it closes the gates 34, 35, and 36 respectively, thereby preventing any new voltages from passing through the lines 33, 36, and 39 to the integrators 265, 266, and 267. Therefore, the voltages in the capacitors 269, 271, and 273 remain whatever they were during the time of the drawing of the preceding bone.

This same operation is true for the bone associated with the parameter gate 52. Thus, with this method, parameter gates are used to stop the bone at any point. This point might normally be the end of another bone which, for example, has drawn the shaft of a cylinder on the end of which it is desired to draw an end plate.

Next, the operation for drawing such an end plate during the time the bone is stationary and essentially a point will be described. The conductors 280', 290, and 294 which carry the output signals from the integrators 265, 266, and 2.67 are fed into the summers 16, 17, and 18 corresponding to the X, Y, and Z components of the display subject. Since the voltages during the drawing of an end plate in the conductors 280, 290, and 294 remain unchanged, the outputs from the summers 16, 17, and 18 will have a DO component voltage representing the X, Y, and Z position of a point in three-dimensional space, as specified by the voltages on the capacitors 269, 271, and 273.

Other inputs to the summers 16, 17, and 18 come through the conductors 28, 29, and 30 from the multipliers 25, 26, and 27. The multipliers are fed simultaneously by signals in the conductor 63 and independently by signals in the conductors 698, 699, and 700. These latter signals are typical of the signals produced in the aforesaid Lee Harrison III Patent No. 3,364,382 except that they represent the cross-sections obtained by scanning only one line of the skin film (the film 341 of that application) in a continuous repetitive fashion. This means that the three signals in the conductors 698, 699, and 700 represent the components X, Y, and Z of a single cross-section of the display subject in three-dimensional space. If these signals were to be repetitively added to the signals in lines 280, 290, and 294, one outer crosssection at the end of a bone would be drawn. However, since the integrators are holding constant voltage outputs corresponding to the end of a bone by virtue of the closing of the gates 34, 37, and 40, the end plate can be drawn by beginning with an extremely small cross-section and expanding it in a spiral. This is done by first establishing a zero voltage in the conductor 63 and gradually increasing it to a value corresponding to 1, as controlled by the ramp function output from the integrator 64. By multiplying signals supplied by the conductors 698, 699, and 700 by the 0 to 1 ramp function voltage, voltages corresponding to the X, Y, and Z coordinates of a spiral are supplied to the summers 16, 17, and 18. These voltages are then transferred to horizontal and vertical deflection voltages in the transform 739 to control the beam of the display oscilloscope 22 in the manner described in the Lee Harrison III Patent No. 3,364,382.

The ramp function is generated in the integrator 64 which has the integrative capacitor 66 across its input. The switch 67 is closed and thus discharges the capacitor 66 unless it is opened by a signal in the conductor 68 which branches from the conductor 48. The signal in the conductor 68 to open the switch 67 is present during the time the gates 51 and 52 are open. When the switch 67 opens, the signal coming from the gate 70 can then be integrated by the integrator 64, thus creating a ramp function which starts at zero and goes to 1. The signals going through the gate 70 are supplied from the ates 73 and 74. The value of the signals in the output conductors 71 and 72 from the gates 73 and 74 will affect the slope of the ramp function generated in the conductor 63. By varying the value of the signals at the conductor inputs 75 and 76 to the gates 73 and 74, the size of the flat plate which is being generated as the end of a bone can be controlled.

Next, the operation for maintaining uniform resolution of the surface, even though the general overall thickness of the display member varies will be described. If the surface of the skin along the longitudinal axis of the display member is essentially parallel to the basic axial vector, the voltages corresponding to the member can be generated at a maximum rate as defined by an acceptable resolution for that member. However, if the angle that the surface of the skin makes with the bone as measured parallel to the longitudinal axis varies the rate of generating the axial or bone vector relative to the rate of generating the volumetric or skin vector must be decreased to provide adequate for producing adequate skin resolution cross-sections.

The angle the surface of the skin makes along the longitudinal axis of the bone is called an average longitudinal derivative. The average longitudinal derivative is a measure of deviations of the surface or skin from being parallel to the bone axis. The purpose of the network in FIGURE 2 is to detect the average longitudinal derivative and use the average longitudinal derivative to control the velocity with which the volumetric vector moves along the basic axial vector. The velocity is controlled by controlling the magnitude of the signal presented to the X, Y, and Z integrators 265, 266, and 267.

The normal basic axial or bone components as described in the aforesaid Lee Harrison III Patent No. 3,364,382 are supplied unmodified in the conductors 277, 287, and 292, and represent the components of velocity set by the overall speed at which the generator 10 works. These signals in the conductors 277, 287, and 292 are fed into the multipliers 12, 13, and 14, respectively. At the same time, signals in the conductors inputs 80, 81, and 82 to the multipliers ranging from zero to one are derived from the average longitudinal derivative information.

The modification of the signals supplied by the conductors 277, 287, and 292 will change the velocity represented by the components of a point describing the bone which appear in the conductors 280, 290, and 294 at the outputs of the integrators 265, 266, and 267.

In FIGURE 2, the three RMS detectors 101, 102, and 103 convert the signals which represent the X, Y, Z components of the surface or skin to signals representing the cross-sections of the display subject and therefore to the gross overall change in the cross-section of any skin pattern longitudinally of the bone. The output conductors 104, 105, and 106 from the RMS detectors 101, 102, and 103 carry signals which are added together in the summer 107 and then fed to the variable attenuator 109. The attenuator 109 permits adjustment of the signal in the conductor 83 to values in the range from zero to one needed to control the multipliers 12, 13, and 14. In this way, the rate of generating the basic axial vector is reduced and varied in relation to variations of the average longitudinal derivative to maintain constant resolution of the surface or skin of the display member.

Another way to generate the average longitudinal derivative as shown in FIGURE 3 functions by passing the skin vector signal as generated by the skin scanner network described in the aforesaid Lee Harrison III Patent No. 3,364,382 (or by other means) through the low pass filter 116. (The low pass filter 116 passes the very low frequency components of the input signal and filters out the rest. The output signals in the conductor 118 are attenuated to values between 0 and 1 in the attenuator 119 and are then fed to the multipliers 12, 13, and 14 of FIGURE 1. When the display subject has a surface or skin of constant circular cross-section as in a vase, this simple approach to obtaining the average longitudinal derivative may be used.

The aver-age longitudinal derivative may also be obtained by the network of FIGURE 5. Here, the conductor carries signals corresponding to the volumetric or skin vector as represented in FIGURE 4. These signals are differentiated in the diiferentiator 131 after which the rectifier 133 produces a negative rectification of the differentiated signal. The negatively rectified signal is fed by the conductor 134 to the attenuator 135 which produces signals in the range of 0 to 1 corresponding to the average longitudinal derivative. Again, these signals 7 are supplied by the conductor 83 to the multipliers 12, 13, and 14.

What is claimed is:

l. A network for controlling surface resolution on a display produced by an electronic image generator comprising means to generate voltages corresponding to the three dimensional coordinates of reference axes of members of a display subject, means to generate voltages corresponding to the three dimensional coordinates of points on the surface of the members, means to synchronize the first generating means with the second generating means, means to integrate the first named voltages to produce ramp functions, and means to control the rate of integration of the first-named voltages in pre-determined correspondence to the rate of generation of the second-named voltages to maintain substantially constant resolution of the surfaces of the members, means to combine the first and second voltages in their respective coordinates, and means to control the production of a display according to the combined voltages.

2. The network of claim 1 including means to resolve the combined three-dimensional coordinate voltages into horizontal and vertical deflection voltages, and means to control the beam of a display device according to the deflection voltages.

3. The network of claim 2 wherein the means to control the rate of integration includes means to hold constant the voltages which are supplied to the integrators, and means to generate expanding values of the second-named voltages during the time the integrator input voltages are held constant.

4. The network of claim 2 wherein the means to control the rate of integration includes a signal corresponding to the average longitudinal derivative of the secondnamed voltages, and means to regulate the rate of supplying the first-named voltages to the integrators according to variations in the average longitudinal derivative signal.

5. The network of claim 4 including a network for producing the average longitudinal derivative signal which comprises an RMS detector for each second coordinate voltage, means to combine the output signals from the RMS detectors.

6. The network of claim 4 including a network for producing the average longitudinal derivative signal which comprises a filter, and means for supplying a signal to the filter corresponding to modulations of a volumetric vector proportioned to the distances of points on the surfaces of the members from their reference axes.

7. The network of claim 4 including a network for producing the average longitudinal derivative signal which comprises a diiferentiator, means for supplying a signal to the differentiator corresponding to modulations of a volumetric vector proportioned to the distances of points on the surfaces of members from their reference axes, and means to produce a negative rectification of the output signal from the diiferentiator.

8. A method of controlling the resolution of surfaces of a display produced by an electronic image generator comprising the steps of generating voltages corresponding to the lengths and positions of three-dimensional coordinates of a reference axis of the display subject, generating voltages corresponding to three-dimensional coordinates of points on the surface of the display subject, integrating the first-named voltages, combining the firstnamed voltages with the second-named voltages, and controlling the rate of integration of the first-named voltages in pre-determined correspondence to variations in the distances of points on the surface of the display subject from the reference axis.

RODNEY D. BENNETT, J'R., Primary Examiner BRIAN L. RIBANDO, Assistant Examiner 

